Abstract: Building sites are created by leveling hills and creating land in the hilly mountainous areas of collapsible loess. The deformation characteristics of the high slopes of excavation and filling and the internal properties of the soil at the exposed position of the boundary line are the key aspect of slope stability evaluation. To investigate the stability of the collapsible loess high slope for the Tongxin Miaoling transformer station from the important hub of the West-East power transmission project, this study conducted field detection tests using professional ground-penetrating radar (GPR) of model pulseEKKO PRO, Survey lines with lengths of 416 m and 372 m were laid at the top of the slope in the excavation area and the fill area. Meanwhile, survey lines of 15 m and 20 m in length were laid on both sides of the excavation and filling boundary. GPR is used to carry out detection work on all survey lines at 0.5 m intervals. The results show that the wave spectrum characteristics image of the high excavation slope is consistent with the soil distribution at the same location in the geological survey results. Meanwhile, its reflected wave is messier, which indicates that there are unloading cracks and sporadic fracture zones inside the slope. There is no abnormal reflective wave surface such as cracks and local subsidence on the high fill slope, and its filling soil is uniform. The original soil in the high fill slope area is self-weight collapsing loess, thus the soil of the high fill slope has potential risks. The boundary area of excavation and filling has a more obvious boundary line of excavation and filling, which has a slow slope and uniform transition. The detection waveform on the side of the boundary line is complex, with many types of lithology, and high soil compactness, while the right side has regular waveforms, single soil properties, low soil compactness, and differences in soil properties between excavation and filling.easily lead to unenen settlement. These results could provide a reference for the design and construction of the high side slope of the cutting hills to the backfill ditch project.